The heads of the UK's largest ISPs have co-signed a letter of protest against the proposal to disconnect suspected illegal file-sharers from their broadband service.

The open letter was sent to The Times on Thursday by the chiefs of TalkTalk, BT, and Orange, as well as representatives of the Open Rights Group and the consumer choice organizations Which and Consumer Focus.

It coincided with a detailed argument against the government's proposals, issued as a statement by the Featured Artists Coalition (FAC), the British Academy of Songwriters, Composers and Authors (Basca) and the Music Producers Guild (MPG).

The signatories of the letter to The Times acknowledged the creative industry's concerns about illegal sharing of copyrighted material. Nevertheless, they said the government's latest proposals on how to reduce this are "misconceived, and threaten broadband consumers' rights and the development of new, attractive services."

"Consumers must be presumed to be innocent unless proven guilty," the letter read. "We must avoid an extrajudicial 'kangaroo court' process where evidence is not tested properly and accused broadband users are denied the right to defend themselves against false accusations.

"Without these protections, innocent customers will suffer. Any penalty must be proportionate. Disconnecting users from the internet would place serious limits on their freedom of expression."

In those proposals, Lord Mandelson's department called for disconnection to be an option in the case of persistent illegal file-sharers.

The proposal came before the deadline on a consultation--launched in June by BIS--into the issue of copyrighted material being shared online. That consultation was kicked off by Lord Carter's Digital Britain report, which discounted the option of disconnection as being unnecessarily harsh.

BIS's proposal suggested ISPs should pay a large portion of the cost of the monitoring and legal mechanisms needed to establish which file-sharers should be disconnected.

The signatories of the letter to The Times pointed out that these costs would filter down to broadband customers. They described the plan as "grossly unfair, since the vast majority of consumers do not file-share illegally."

Also on Thursday, the FAC, Basca, and MPG issued a joint statement arguing that a system where suspected illegal file-sharers are monitored, sent warning letters, and punished would not lead to a "vibrant, functional, fair, and competitive" market for music.

"As a result, we believe that the specific questions asked by the consultation are not only unanswerable, but indicate a mindset so far removed from that of the general public and music consumer that it seems an extraordinarily negative document," the organizations wrote.

The organizations argued that the consultation's estimate for the damage done to the content industries by file-sharing--about $328 million per year--was based upon the premise that a P2P-downloaded track equals a lost sale. Therefore, the estimate is no more than "'lobbyists' speak' (as) it has little support from logic, and no economist would seek to weave such a number into a metric aimed at quantifying a 'value gap' for the industries challenged by P2P," they said.

The organizations also noted the costs of monitoring for illegal file-sharing, and said the consultation's estimate of $92 million to $139 million was likely to be a gross underestimate due to the complicated nature of the proposed system.

"Looking backward for insight into how we adapt mass-production product models to the digital age of access and services has been a major obstacle to progress over the past decade," they wrote. "We must begin to look forward to business models that we cannot even imagine yet.

"As creators' representatives, we are willing to be partners with government in exploring and navigating the opportunities and challenges brought by digital technologies. What we will not be a party to is any system that alienates our members' existing audience and potential new audiences."